Sintering Temperature Effects on Structural, Magnetic, Magnetocaloric and Critical Properties of Nd0.67Pb0.33Mn0.9Al0.1O3 Manganites

We have reported the results of structural, magnetic, and magnetocaloric characterizations as well as the critical behaviors of the polycrystalline Nd0.67Pb0.33Mn0.9Al0.1O3 manganites. These samples, denoted as S900 and S1100, were prepared using the sol–gel method and sintered separately at 900 °C and 1100 °C, respectively. XRD analysis shows good crystallization for the samples in the R3¯c\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ R\overline{3}c $$\end{document} rhombohedral structure. From M(T) curves, second-order ferromagnetic–paramagnetic (FM–PM) phase transitions appear at the Curie temperatures (TC) around 130 K and 155 K for S900 and S1100, respectively. The estimated values of magnetic entropy change (−ΔSm) at μ0H = 5 T were found to be 3.23 and 4.41 J/kg.K for S900 and S1100, respectively. The corresponding values of relative cooling power (RCP) are equal to 242 and 245 J/kg. These values are relatively higher, making our samples promising candidates for magnetic refrigeration technology. We found that the critical exponents (β, γ, and δ) agree well with those of the mean-field and the 3D-Heisenberg models for S900 and S1100, respectively.